Section [ Actinotaenium ]: Cell body cylindrical, slightly constricted at the center, cell surface smooth or dotted or punctated (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Cell body small, 22-(32-43)-60 μm long, 10.5-(20-23)-32 μm wide, isthmus 9.5-(18-21.5)-30 μm wide, L/W=2; semicells ovoidal; (Illustrations of the Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: standing water on a bank under Kurome-gawa-bashi (bridge), Kurome River, Asaka city, Saitama Pref., December 10, 2006, by Y. Tsukii